Linking habitat quality with genetic diversity: a lesson from great bustards in Spain

P. 411-419The effects of habitat loss and fragmentation on the genetic structure and variability of wild populations have received wide empirical support and theoretical formalization. By contrast, the effects of habitat quality seem largely underinvestigated, partly due to technical difficulties in properly assessing habitat quality. In this study, we combine geographic information system (GIS)-based habitat-quality modelling with a landscape genetics approach based on mitochondrial DNA markers to evaluate the possible influence of habitat quality on the levels and distribution of genetic diversity in a range of natural populations (n = 15) of Otis tarda throughout Spain. Ninety-three percent of the population represented by our countrywide sample lives in good-quality habitats, while 4.5% and 2.5% occur respectively in intermediate and poor habitats. Habitat quality was highly correlated with patch size, population size and population density, indicating the reliability and predictive power of the habitat suitability model. Genetic diversity was significantly correlated with habitat quality, size and density of the population, but not with patch size. Three of a total of 20 existing matrilineages from the species’ current genetic pool are restricted to poor-quality habitats. This study therefore highlights the importance of considering both population genetics and habitat quality in a species of high conservation priority.S

Update on the Combined Analysis of Muon Measurements from Nine Air Shower Experiments

Over the last two decades, various experiments have measured muon densities in extensive air showers over several orders of magnitude in primary energy. While some experiments observed differences in the muon densities between simulated and experimentally measured air showers, others reported no discrepancies. We will present an update of the meta-analysis of muon measurements from nine air shower experiments, covering shower energies between a few PeV and tens of EeV and muon threshold energies from a few 100 MeV to about 10GeV. In order to compare measurements from different experiments, their energy scale was cross-calibrated and the experimental data has been compared using a universal reference scale based on air shower simulations. Above 10 PeV, we find a muon excess with respect to simulations for all hadronic interaction models, which is increasing with shower energy. For EPOS-LHC and QGSJet-II.04 the significance of the slope of the increase is analyzed in detail under different assumptions of the individual experimental uncertainties

Search for Spatial Correlations of Neutrinos with Ultra-high-energy Cosmic Rays

For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for correlating the arrival directions of neutrinos with the arrival directions of UHECRs. The neutrino data are provided by the IceCube Neutrino Observatory and ANTARES, while the UHECR data with energies above ∼50 EeV are provided by the Pierre Auger Observatory and the Telescope Array. All experiments provide increased statistics and improved reconstructions with respect to our previous results reported in 2015. The first analysis uses a high-statistics neutrino sample optimized for point-source searches to search for excesses of neutrino clustering in the vicinity of UHECR directions. The second analysis searches for an excess of UHECRs in the direction of the highest-energy neutrinos. The third analysis searches for an excess of pairs of UHECRs and highest-energy neutrinos on different angular scales. None of the analyses have found a significant excess, and previously reported overfluctuations are reduced in significance. Based on these results, we further constrain the neutrino flux spatially correlated with UHECRs

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Passage marker excretion in red kangaroo (Macropus rufus), collared peccary (Pecari tajacu) and colobine monkeys (Colobus angolensis, C. polykomos, Trachypithecus johnii)

Ruminants are characterised by an efficient particle sorting mechanism in the forestomach followed by selective rechewing of large food particles. For the non-ruminating foregut fermenter pygmy hippo it was demonstrated that large particles are excreted as fast as, or faster than, the small particles. The same has been suggested for other non-ruminating foregut fermenters. We determined the mean retention time of fluids and different sized particles in six red kangaroos (Macropus rufus), seven collared peccaries (Pecari tajacu) and three colobine monkeys (Colobus angolensis, C. polykomos, Trachypithecus johnii). We fed Co-EDTA as fluid and mordanted fibre as particle markers (Cr, Ce). Mean (± SD) total tract retention time for fluids, small and large particles was 14±2 h, 29±10 h and 30±9 h in red kangaroos, 26±2 h, 34±5 h and 32±3 h in collared peccaries and 57±17 h, 55±19 h and 54±19 h in colobine monkeys, respectively. Large and small particles were excreted simultaneously in all species. There was no difference in the excretion of fluids and particles in the colobine monkeys, in contrast to the other foregut fermenters. In the non-primate, non-ruminant foregut fermenters, the difference in the excretion of fluids and small particles decreases with increasing food intake. In contrast, ruminants keep this differential excretion constant at different intake levels. This may be a prerequisite for the sorting of particles in their forestomach and enable them to achieve higher food intake rates. The functional significance of differential excretion of fluids and particles from the forestomach requires further investigations

More efficient mastication allows increasing intake without compromising digestibility or necessitating a larger gut: Comparative feeding trials in banteng (Bos javanicus) and pygmy hippopotamus (Hexaprotodon liberiensis)

The digestion of plant material in mammalian herbivores basically depends on the chemical and structural composition of the diet, the mean particle size to which the forage is processed, and the ingesta retention time. These different factors can be influenced by the animal, and they can presumably compensate for each other. The pygmy hippopotamus, a non-ruminating foregut fermenter, has longer mean retention times than ruminants; however hippos do not achieve higher (fibre) digestibilities on comparable diets, which could be due to ineffective mastication. We performed feeding trials with six pygmy hippos (Hexaprotodon liberiensis) and six banteng cattle (Bos javanicus) on a grass diet. As predicted, both species achieved similar dry matter, organic matter, crude protein and gross energy digestibilities. However, neutral and acid detergent fibre digestibility was lower in pygmy hippos. Apparently, in these species, fibre digestibility was more influenced by particle size, which was larger in pygmy hippos compared to banteng, than by retention time. In spite of their higher relative food intake, the banteng in this study did not have greater relative gut fills than the hippos. Ruminants traditionally appear intake-limited when compared to equids, because feed particles above a certain size cannot leave the rumen. But when compared to nonruminating foregut fermenters, rumination seems to free foregut fermenters from an intrinsic food intake limitation. The higher energy intakes and metabolic rates in wild cattle compared to hippos could have life-history consequences, such as a higher relative reproductive rate

Excretion patterns of fluid and different sized particle passage markers in banteng (Bos javanicus) and pygmy hippopotamus (Hexaprotodon liberiensis): two functionally different foregut fermenters

Processing of ingesta particles plays a crucial role in the digestive physiology of herbivores. In the ruminant forestomach different sized particles are stratified into a small and a large particle fraction and only the latter is regurgitated and remasticated to smaller, easier-to-digest particles. In contrast, it has been suggested that in non-ruminating foregut fermenters, such as hippopotamuses, larger particles should be selectively excreted since they tend to be digested at a slower rate and hence can be considered intake-limiting bulk. In our study we determined the mean retention time (MRT) of fluids and different sized particles (2 mm and 10 mm) in six pygmy hippos (Hexaprotodon liberiensis) and six banteng (Bos javanicus) on a diet of fresh grass at two intake levels. We used cobalt ethylendiamintetraacetate (Co-EDTA) as fluid and chromium (Cr)-mordanted fibre (2 mm) and cerium (Ce)-mordanted fibre (10 mm) as particle markers, mixed in the food. Average total tract MRT for fluid, small and large particles at the high intake level was 32, 76 and 73 h in pygmy hippos and 25, 56 and 60 h in banteng, and at the low intake level 39, 109, and 105 h in pygmy hippos and 22, 51 and 58 h in banteng, respectively. In accordance with the prediction, large particles moved faster than, or as fast as the small particles, through the gut of pygmy hippos. In contrast, large particles were excreted slower than the small particles in the ruminant of this study, the banteng. Pygmy hippos had longer retention times than the banteng, which probably compensate for the less efficient particle size reduction. Although the results were not as distinct as expected, most likely due to the fact that ingestive mastication of the larger particle marker could not be prevented, they confirm our hypothesis of a functional difference in selective particle retention between ruminating and non-ruminating foregut fermenters

Particle retention in the forestomach of a browsing ruminant, the roe deer capreolus capreolus

A combination of a flotation/sedimentation experiment and sieve analysis for the reticulorumen (RR) contents of roe deer Capreolus capreolus Linnaeus, 1758, a browsing ruminant, showed that there was no correlation between particle size and particle density. Large particles were present in both the sedimented and the buoyant fraction, which is in accord with the reported absence of stratification of RR contents in browsing ruminants. Comparative sieve analysis of roe deer RR and caecal/rectal material demonstrated that there must be some selective particle retention in the browsing ruminant as well, as a certain fraction of large particles in RR contents does not occur in the caecal/rectal material. These results lead to the explanatory dilemma that, while selective particle retention is observed, it cannot be due to the mechanisms known to work in grazing ruminants